What is the meaning of Naperoun?

An apron or smock (garment worn over torso)

A bishop's apron; a short cassock.

Jordan, Richard (1974)  Eugene Crook, transl., Handbook of the Middle English Grammar: Phonology (Janua Linguarum; 214), The Hague: Mouton & Co. N.V., →DOI, § 171, page 161.

nāprō̆n, n.”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.

Source: wiktionary.org